Study of Co(II) adsorption from aqueous solution using protein granules produced from chicken feather

Background: Co(II) constitutes a part of vitamin B12, hence, it is necessary for human health. However, at concentrations higher than the permissible limits, humans and animals suffer adverse chronic effects. It is necessary to reduce the concentration to a permissible level. In the present study, pre-purification and thermal modification of chicken's feather increased their porosity and they were used to adsorb Co(II) ions from aqueous solutions. Methods: Chicken feather was procured from a slaughter house, washed with detergent and dried at laboratory temperature. To increase the porosity and remove the organic pollutants attached to the feather, feathers were heated in the oven for 1 hour at 165°C. Some batch experiments were conducted to optimize the parameters affecting the adsorption process, such as solution pH, initial concentration of Co(II) and contact time, at a constant agitating speed and temperature. Results: The pHzpc of chicken's feather granules obtained was 5.3. The results showed that a time of 60 minutes, pH value of 9 and initial concentration of 10 mg/l were the optimum conditions for Co(II) removal by the adsorption process. Increasing the initial concentration of Co(II) from 10 to 50 decreased the removal efficiency from 52% to 26%. The pseudo-first order kinetic model provided the best correlation (R2 = 0.998) for adsorption of Co(II) on chicken's feather granules. Conclusion: The increase in electrostatic repulsion forces between positive charges of Co(II) ions decreased the removal efficiency at higher concentrations of Co(II) ions. The maximum efficiency of Co(II) adsorption was obtained at pH= 9, which is higher than the pHzpc of the adsorbent.